Patent Document 1 discloses a valve driving device for an engine in which rocker arms are mounted at both sides of a swing arm that moves around a rocker shaft as a swing fulcrum. In this device, the swing arm swings according to the rotation of a cam to allow the rocker arms to simultaneously drive valves (intake valves or exhaust valves). In this device, the swing arm is supported to be capable of moving up and down to allow a valve timing to be changed into plural cases.